United's attacking options are thin on the ground after the club decided against taking up the option of signing Radamel Falcao permanently following his Old Trafford loan spell last season, while Robin van Persie left to join Fenerbahce last week.
Memphis Depay won the Golden Boot in Holland with 23 goals for PSV
Falcao has joined Chelsea on a similar season-long loan deal and United now are left with relatively unproven youngster James Wilson, and Javier Hernandez - who spent last season on loan at Real Madrid - as striking alternatives to Rooney if the United skipper is unavailable.
New signing Memphis Depay, who joined from PSV after finishing top scorer in the Dutch Eredvisie last season, could also be used as a lone striker if Louis van Gaal's side line up in a 4-3-3 formation next term.
Rooney scored 12 Premier League goals last season and has failed to score more than 20 in the league since the 2011/12 campaign, when he scored 27 and finished behind just Arsenal's Van Persie in the Premier League top scorer stakes.
The England captain was deployed by Van Gaal in central midfield and in a number 10 role on several occasions last season and has also played in wide roles in recent years but after being named as United captain last season, he is now expected to be handed a senior striking role.
Javier Hernandez could be given a chance to impress in pre-season after last season's loan spell at Real Madrid
Van Gaal is thought to be relaxed about the striker situation and is expected to give Hernandez a chance to get his Old Trafford career back on track if another centre forward is not signed.
United have already spent £80m this summer bringing in Depay, midfielders Bastian Schweinsteiger and Morgan Schneiderlin, and full-back Matteo Darmian from Torino.
